byte-engine 0.1.0

A composable Rust game engine focused on graphics, input, audio, physics, and retained UI.
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View: struct {
	view: mat4f,
	projection: mat4f,
	view_projection: mat4f,
	inverse_view: mat4f,
	inverse_projection: mat4f,
	inverse_view_projection: mat4f,
	fov: vec2f,
	near: f32,
	far: f32,
}

Mesh: struct {
	model: mat4x3f,
	material_index: u32,
	base_vertex_index: u32,
	base_primitive_index: u32,
	base_triangle_index: u32,
	base_meshlet_index: u32,
	meshlet_count: u32,
	skinned_base_vertex_index: u32,
	padding0: u32,
}

Meshlet: struct {
	primitive_offset: u32,
	triangle_offset: u32,
	primitive_count: u32,
	triangle_count: u32,
	center_radius: vec4f,
	cone_apex_cutoff: vec4f,
	cone_axis: vec4f,
}

SkinnedVertex: struct {
	position: vec4f,
	normal: vec4f,
}

Views: struct {
	views: View[8],
}

Meshes: struct {
	meshes: Mesh[1024],
}

VertexPositions: struct {
	positions: vec3f[262144],
}

SkinnedVertices: struct {
	vertices: SkinnedVertex[262144],
}

VertexIndices: struct {
	vertex_indices: u16[262144],
}

PrimitiveIndices: struct {
	primitive_indices: u8[786432],
}

Meshlets: struct {
	meshlets: Meshlet[4096],
}

views: descriptor<Views, 0, read>;
meshes: descriptor<Meshes, 1, read>;
vertex_positions: descriptor<VertexPositions, 2, read>;
skinned_vertices: descriptor<SkinnedVertices, 4, read>;
vertex_indices: descriptor<VertexIndices, 6, read>;
primitive_indices: descriptor<PrimitiveIndices, 7, read>;
meshlets: descriptor<Meshlets, 8, read>;

meshlet_indices: task_payload<u32, 32>;
out_instance_index: output<u32, 0, 126>;
out_primitive_index: output<u32, 1, 126>;

push_constant: push_constant {
	instance_index: u32,
	view_index: u32,
}

main: fn() -> void {
	let mesh: Mesh = meshes.meshes[push_constant.instance_index];
	let view: View = views.views[push_constant.view_index];
	let meshlet_index: u32 = meshlet_indices[threadgroup_position()];
	let meshlet: Meshlet = meshlets.meshlets[meshlet_index];
	let primitive_index: u32 = thread_idx();

	if (primitive_index == 0) {
		set_mesh_output_counts(meshlet.primitive_count, meshlet.triangle_count);
	}

	if (primitive_index < meshlet.primitive_count) {
		let relative_vertex_index: u32 = u32(vertex_indices.vertex_indices[
			mesh.base_primitive_index + meshlet.primitive_offset + primitive_index
		]);
		let vertex_index: u32 = mesh.base_vertex_index + relative_vertex_index;
		let position: vec4f = vec4f(
			vertex_positions.positions[vertex_index].x,
			vertex_positions.positions[vertex_index].y,
			vertex_positions.positions[vertex_index].z,
			1.0
		);
		if (mesh.skinned_base_vertex_index != 4294967295) {
			position = skinned_vertices.vertices[mesh.skinned_base_vertex_index + relative_vertex_index].position;
		}

		let world_position: vec3f = mesh.model * position;
		set_mesh_vertex_position(
			primitive_index,
			view.view_projection * vec4f(world_position.x, world_position.y, world_position.z, 1.0)
		);
	}

	if (primitive_index < meshlet.triangle_count) {
		let triangle_base_index: u32 = mesh.base_triangle_index + meshlet.triangle_offset + primitive_index;
		set_mesh_triangle(
			primitive_index,
			vec3u(
				u32(primitive_indices.primitive_indices[triangle_base_index * 3 + 0]),
				u32(primitive_indices.primitive_indices[triangle_base_index * 3 + 1]),
				u32(primitive_indices.primitive_indices[triangle_base_index * 3 + 2])
			)
		);
		out_instance_index[primitive_index] = push_constant.instance_index;
		out_primitive_index[primitive_index] = (meshlet_index << 8) | (primitive_index & 255);
	}
}